In the manufacturing and packaging of laser diodes, it is a common practice to place the laser diode in a standard electronic device housing such as a TO housing, and to include a photodiode or other photosensor within the housing. The laser diode device generally includes parallel mirror surfaces that define the resonant cavity of the laser, with one of the mirror surfaces totally reflective and the other, partially reflective mirror surface comprising the output of the laser diode. Although the one mirror surface is generally considered to be completely reflective, a small amount of the laser light is transmitted therethrough. The photodiode is placed adjacent to the totally reflective mirror surface to receive the light leaking through the mirror surface. The current through the photodiode is proportional to the output of the laser diode. The photodiode may be connected to an external circuit that controls the laser diode output, so that a feedback loop is established that very accurately controls the power output of the laser diode.
As development of laser diode devices has advanced in recent years, the maximum power output has increased markedly. Laser diodes are now sufficiently powerful to be used for medical treatment, such as, but not limited to, ophthalmic procedures, dental procedures, and irradiation of tissue for purposes of wound healing, pain relief, and anesthesia. A potential problem concomitant with the use of more powerful laser diode devices is that the beam projected by a device may pose a safety hazard, especially regarding the eyes of personnel in the general vicinity of laser use. This problem is compounded by the fact that most high power laser diodes currently available operate in the infrared band, and are not visible to the human eye. Therefor, it is essential that the laser diode device be directed toward an intended target, and be prevented from emitting a free beam that can cause harm at large distances.
Moreover, it is beneficial to know that the delivery path of the laser device is free of dirt, oil and other debris that can scatter the laser output and diminish the effectiveness of the laser treatment. If the laser device operates in the visible spectrum, the scattering effect is easily visualized. However, an invisible laser beam may be scattered or attenuated by dirt and the like without being observed, and the effectiveness of the laser treatment may suffer without apparent cause. Thus, a system for warning of laser beam scattering or attenuation in the delivery path would be very useful for infrared laser devices.
It is an object of the invention to provide a proximity device to enable laser diode operation. It is a further object to utilize the photodiode generally included in the laser diode housing to form a proximity sensor. More specifically, an object of the invention is to detect whether or not an object is proximate to the output window of the laser diode, and to permit operation of the laser diode only when an object is sufficiently proximate to receive the laser output beam in point blank fashion. A further object of the invention is to use the photodiode in the laser diode housing to detect the scattering, blocking, or attenuation of the laser output, and warn the user of these conditions so that the delivery path may be cleared or cleaned when required.